﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace XLB.FileDownLoad
{
    public partial class FileDownload : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string fileName = System.Configuration.ConfigurationManager.AppSettings["filename"];//客户端保存的文件名
            string filePath = Server.MapPath("~/file/" + System.Configuration.ConfigurationManager.AppSettings["filename"]);//路径
            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
            if (fileInfo.Exists)
            {
                //设置文件下载的最大下载量

                const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力
                byte[] buffer = new byte[ChunkSize];
                Response.Clear();
                System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
                long dataLengthToRead = iStream.Length;//获取下载的文件总大小
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
                Response.AddHeader("Content-Length", iStream.Length.ToString());
                while (dataLengthToRead > 0 && Response.IsClientConnected)
                {
                    int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
                    Response.OutputStream.Write(buffer, 0, lengthRead);
                    Response.Flush();
                    dataLengthToRead = dataLengthToRead - lengthRead;
                }
                Response.Close();
            }
        }
    }
}